Ent-trachyloban-19-oic acid isolated from Iostephane heterophylla as a promising antibacterial agent against Streptococcus mutans biofilms

Antibacterial and Antifungal Terpenes from the Medicinal Angiosperms of Asia and the Pacific: Haystacks and Gold Needles

This review identifies terpenes isolated from the medicinal Angiosperms of Asia and the Pacific with antibacterial and/or antifungal activities and analyses their distribution, molecular mass, solubility, and modes of action. All data in this review were compiled from Google Scholar, PubMed, Science Direct, Web of Science, ChemSpider, PubChem, and library searches from 1968 to 2022. About 300 antibacterial and/or antifungal terpenes were identified during this period. Terpenes with a MIC ≤ 2 µg/mL are mostly amphiphilic and active against Gram-positive bacteria, with a molecular mass ranging from about 150 to 550 g/mol, and a polar surface area around 20 Ų. Carvacrol, celastrol, cuminol, dysoxyhainic acid I, ent-1β,14β-diacetoxy-7α-hydroxykaur-16-en-15-one, ergosterol-5,8-endoperoxide, geranylgeraniol, gossypol, 16α-hydroxy-cleroda-3,13 (14)Z-diene-15,16-olide, 7-hydroxycadalene, 17-hydroxyjolkinolide B, (20R)-3β-hydroxy-24,25,26,27-tetranor-5α cycloartan-23,21-olide, mansonone F, (+)-6,6'-methoxygossypol, polygodial, pristimerin, terpinen-4-ol, and α-terpineol are chemical frameworks that could be candidates for the further development of lead antibacterial or antifungal drugs.

Ethnobotany and the Role of Plant Natural Products in Antibiotic Drug Discovery

The crisis of antibiotic resistance necessitates creative and innovative approaches, from chemical identification and analysis to the assessment of bioactivity. Plant natural products (NPs) represent a promising source of antibacterial lead compounds that could help fill the drug discovery pipeline in response to the growing antibiotic resistance crisis. The major strength of plant NPs lies in their rich and unique chemodiversity, their worldwide distribution and ease of access, their various antibacterial modes of action, and the proven clinical effectiveness of plant extracts from which they are isolated. While many studies have tried to summarize NPs with antibacterial activities, a comprehensive review with rigorous selection criteria has never been performed. In this work, the literature from 2012 to 2019 was systematically reviewed to highlight plant-derived compounds with antibacterial activity by focusing on their growth inhibitory activity. A total of 459 compounds are included in this Review, of which 50.8% are phenolic derivatives, 26.6% are terpenoids, 5.7% are alkaloids, and 17% are classified as other metabolites. A selection of 183 compounds is further discussed regarding their antibacterial activity, biosynthesis, structure-activity relationship, mechanism of action, and potential as antibiotics. Emerging trends in the field of antibacterial drug discovery from plants are also discussed. This Review brings to the forefront key findings on the antibacterial potential of plant NPs for consideration in future antibiotic discovery and development efforts.

Divergent Evolution of the Diterpene Biosynthesis Pathway in Tea Plants (Camellia sinensis) Caused by Single Amino Acid Variation of ent-Kaurene Synthase

Most plant terpenoids are classified as secondary metabolites. A small portion of them are products of primary metabolism biosynthesized by relatively conserved pathways. Gibberellins (GAs), which are essential for plant growth and development, are diterpenoid phytohormones. (E,E,E)-Geranylgeranyl diphosphate (GGPP) is the precursor for both GAs and other diterpenoids of secondary metabolism. ent-Kaurene biosynthesis from GGPP is a key step of GA formation, which is catalyzed by two sequential and dedicated diterpene synthases (diTPSs): ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase (KS) of the terpene synthase gene family. Sharing a common evolutionary origin, CPS and KS belong to different TPS subfamilies. Tea plant (Camellia sinensis), the subject of this study, is a leaf-based economic crop. Budbreak mainly manipulated by GAs is a primary factor for targeted tea breeding. The key genes for gibberellin biosynthesis are known; however, they have not yet been characterized in tea plants. Here, we identified and functionally characterized three diterpene biosynthesis-related genes, including one CPS and two highly similar KSs in tea plants. These genes were initially identified through transcriptome sequencing. The functional characterization determined by enzymatic activity assay indicated that CsCPS could catalyze GGPP to form ent-copalyl diphosphate (ent-CPP), which was further used as the substrate by CsKS1 to produce ent-kaurene or by CsKS2 to produce 16α-hydroxy-ent-kaurane with ent-kaurene as a minor product, respectively. We demonstrated that the divergent evolution of diterpene biosynthesis in tea plants resulted from gene duplication of KSs, followed by functional divergence caused by single amino acid variation. This study would provide an insight into the diterpenoid metabolism and GA biosynthesis in tea plants to further understand leaf bud development or insect resistance and to provide a genetic basis for tea plant breeding.

Critical evaluation of current Alzheimer's drug discovery (2018-19) & futuristic Alzheimer drug model approach

Alzheimer's disease (AD), a neurodegenerative disease responsible for death of millions of people worldwide is a progressive clinical disorder which causes neurons to degenerate and ultimately die. It is one of the common causes of dementia wherein a person's incapability to independently think, behave and decline in social skills can be quoted as major symptoms. However the early signs include the simple non-clinical symptoms such as forgetting recent events and conversations. Onset of these symptoms leads to worsened conditions wherein the AD patient suffers severe memory impairment and eventually becomes unable to work out everyday tasks. Even though there is no complete cure for AD, rigorous research has been going on to reduce the progress of AD. Currently, a very few clinical drugs are prevailing for AD treatment. So this is the need of hour to design, develop and discovery of novel anti-AD drugs. The main factors for the cause of AD according to scientific research reveals structural changes in brain proteins such as beta amyloid, tau proteins into plaques and tangles respectively. The abnormal proteins distort the neurons. Despite the high potencies of the synthesized molecules; they could not get on the clinical tests up to human usage. In this review article, the recent research carried out with respect to inhibition of AChE, BuChE, NO, BACE1, MAOs, Aβ, H3R, DAPK, CSF1R, 5-HT4R, PDE, σ₁R and GSK-3β is compiled and organized. The summary is focused mainly on cholinesterases, Aβ, BACE1 and MAOs classes of potential inhibitors. The review also covers structure activity relationship of most potent compounds of each class of inhibitors alongside redesign and remodeling of the most significant inhibitors in order to expect cutting edge inhibitory properties towards AD. Alongside the molecular docking studies of the some final compounds are discussed.

Effect of Side Chain Functional Groups on the DPPH Radical Scavenging Activity of Bisabolane-Type Phenols

Methods for improving the antioxidant activity of phenolic compounds have been widely investigated; however, most studies have focused on the structure⁻activity correlations of substituents on the aromatic rings of catechols or flavonoids. We investigated the influence of side chain functional groups on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of xanthorrhizol and curcuphenol analogues. These compounds were synthesised by the side chain functional group conversion of curcumene, followed by direct oxidation of the aromatic ring. We determined the DPPH radical scavenging activity from the half-maximal effective concentration (EC₅₀) obtained from a DPPH assay in methanol. The positional relationships of the side chain with the aromatic ring and phenolic OH group were determined using density functional theory calculations, and the stability of different conformations was compared. Electron transfer-proton transfer was determined to be the dominant mechanism in the DPPH reaction with xanthorrhizol analogues, based on the correlation between the EC₅₀ and ionisation potential. The radical cation was greatly stabilised in the structure where the side chain functional group was close to the aromatic ring. Stabilisation also depended on the phenolic OH group position. In future antioxidant design, aromatic ring substituent conversion and the use of functional groups far from the OH group or ring should be explored.

Plant Natural Products Targeting Bacterial Virulence Factors

Decreased antimicrobial efficiency has become a global public health issue. The paucity of new antibacterial drugs is evident, and the arsenal against infectious diseases needs to be improved urgently. The selection of plants as a source of prototype compounds is appropriate, since plant species naturally produce a wide range of secondary metabolites that act as a chemical line of defense against microorganisms in the environment. Although traditional approaches to combat microbial infections remain effective, targeting microbial virulence rather than survival seems to be an exciting strategy, since the modulation of virulence factors might lead to a milder evolutionary pressure for the development of resistance. Additionally, anti-infective chemotherapies may be successfully achieved by combining antivirulence and conventional antimicrobials, extending the lifespan of these drugs. This review presents an updated discussion of natural compounds isolated from plants with chemically characterized structures and activity against the major bacterial virulence factors: quorum sensing, bacterial biofilms, bacterial motility, bacterial toxins, bacterial pigments, bacterial enzymes, and bacterial surfactants. Moreover, a critical analysis of the most promising virulence factors is presented, highlighting their potential as targets to attenuate bacterial virulence. The ongoing progress in the field of antivirulence therapy may therefore help to translate this promising concept into real intervention strategies in clinical areas.

Natural products and caries prevention

Dental caries is considered as the most common polymicrobial oral disease in the world. With the aim of developing alternative approaches to reduce or prevent the decay, numerous papers showed the potential anticaries activity of a number of natural products. The natural products with anticaries effects are selected from e.g. food, beverages, flowers or traditional herbs. Most of the effective components are proven to be polyphenol compounds. Many of the natural products are studied as antibacterial agents, while some of them are found to be effective in shifting the de-/remineralization balance. However, the mechanisms of the anticaries effects are still unclear for most of the natural products. In the future, more efforts need to be made to seek novel effective natural products via in vitro experiment, animal study and in situ investigations, as well as to enhance their anticaries effects with the help of novel technology like nanotechnology.